JP2006131062A - Suspension device and suspension control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively restrain change of a posture by controlling a suspension at good response. <P>SOLUTION: This suspension suspending a wheel can adjust a suspension characteristic giving an influence to change of the posture of a vehicle body. A detection part 8 directly detects a vertical load acting on the wheel. A first sensor 9 detects a vehicle condition volume indicating a condition of the vehicle. A second sensor 10 detects an operation condition volume indicating an operation condition of a driver. An estimation part 70 estimates the vertical load from the detected vehicle condition volume and operation condition volume based on a vehicle movement model modeling behaviors of the vehicle. A control unit 71 compares the detected vertical load with the estimated vertical load, and controls the suspension characteristic based on the results of comparison. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a suspension device and a suspension control method.

2. Description of the Related Art Conventionally, suspension devices that control suspension characteristics dynamically and suppress changes in the posture of a vehicle body are known from the viewpoint of improving ride comfort or vehicle operability (for example, Patent Documents). 1). In this type of suspension device, the load movement accompanying the operation of the driver is specified from the stroke amount of the suspension because the suspension characteristics are controlled based on the vertical load acting on the wheel. Then, suspension characteristics such as a damping force of the damper and a spring force of the suspension are controlled so that this stroke amount becomes the target stroke amount.
JP-A-11-42918

  However, the method of detecting the stroke amount of the suspension has a problem that the load movement, that is, the force for changing the posture of the vehicle body cannot be captured unless the posture change occurs, and the control responsiveness is low. .

  Accordingly, an object of the present invention is to effectively suppress a change in posture by performing suspension control with high responsiveness.

  In order to solve this problem, the first invention provides a suspension device. The suspension device includes a suspension capable of suspending a wheel and adjusting a suspension characteristic that affects a change in posture of the vehicle body, a detection unit that directly detects a vertical load acting on the wheel, and a vehicle that indicates a state of the vehicle. A first sensor that detects a state quantity, an estimation unit that estimates a vertical load from the detected vehicle state quantity based on a vehicle motion model that models the behavior of the vehicle, and a detected vertical load. And a control unit that controls suspension characteristics based on the comparison result.

  The second invention provides a suspension device. This suspension device suspends a wheel and can adjust a suspension characteristic that affects the posture change of the vehicle body, a detection unit that directly detects a longitudinal force, a lateral force, and a vertical load acting on the wheel, Based on the vehicle specifications and at least the detected longitudinal force or the detected lateral force, the estimation unit for estimating the vertical load by estimating the vehicle state quantity indicating the state of the vehicle, the detected vertical load, A control unit that compares the estimated vertical load and controls suspension characteristics based on the comparison result.

  Here, in the first invention or the second invention, when the detected vertical load is smaller than the estimated vertical load, the control unit controls the suspension characteristics so that the suspension resists the displacement toward the contraction side. However, when the detected vertical load is larger than the estimated vertical load, it is preferable to control the suspension characteristics so that the suspension resists displacement toward the extension side.

  In the first invention or the second invention, the suspension may have a damper capable of adjusting a damping force as a suspension characteristic. In this case, when the detected vertical load is smaller than the estimated vertical load, the control unit increases the damping force of the damper from the current state, and the detected vertical load is larger than the estimated vertical load. In this case, it is preferable to make the damping force of the damper smaller than the current state as suspension characteristics.

  In the first invention or the second invention, the suspension may be a suspension that can adjust a spring force as a suspension characteristic. In this case, when the detected vertical load is smaller than the estimated vertical load, the control unit increases the spring force from the current state, and when the detected vertical load is larger than the estimated vertical load, It is preferable to make the spring force smaller than the current state.

  Furthermore, in the first invention or the second invention, a second sensor for detecting an operation state amount of the driver may be further included. In this case, the estimation unit estimates the vertical load based on the previously described vehicle state quantity and the detected operation state quantity.

  The third invention provides a suspension control method. The suspension control method includes a first step for directly detecting a vertical load acting on a wheel, a second step for detecting a vehicle state quantity indicating the state of the vehicle, and a vehicle motion modeling the behavior of the vehicle. Based on the model, the third step of estimating the vertical load from the detected vehicle state quantity is compared with the detected vertical load and the estimated vertical load, and the suspension for suspending the wheel based on the comparison result And a fourth step of controlling suspension characteristics that affect the posture change of the vehicle body.

  Here, in the third invention, in the fourth step, when the detected vertical load is smaller than the estimated vertical load, the suspension characteristics are controlled and estimated so that the suspension resists the displacement toward the contraction side. In the case where the detected vertical load is larger than the detected vertical load, it is preferable to control the suspension characteristics so that the suspension resists displacement toward the extension side.

  According to the present invention, the directly detected vertical load is compared with the vertical load estimated by the vehicle motion model, and the suspension characteristics are controlled based on the comparison result. In the direct detection, the vertical load can be detected before the posture change occurs. Therefore, the control response can be enhanced by controlling the suspension characteristics with reference to this value. Thereby, the posture change accompanying cornering and acceleration / deceleration, and the posture change accompanying road surface unevenness | corrugation can be suppressed effectively.

  FIG. 1 is an explanatory diagram of a vehicle to which the suspension device A according to the present embodiment is applied. This vehicle is a four-wheel drive vehicle in which front, rear, left and right four wheels are driven. Power from a crankshaft (not shown) of the engine 1 is transmitted to a front wheel side and a rear wheel side drive shaft (axle) 4 via an automatic transmission 2 and a center differential device 3, respectively. When power is transmitted to the axle 4, a driving torque is applied to each wheel 5, thereby applying a driving force to the wheel 5.

  The individual wheels 5 are respectively suspended by suspensions 6 capable of adjusting suspension characteristics that affect the posture change of the vehicle body. The suspension 6 includes a spring 60, a damping force variable shock absorber (hereinafter referred to as "damper") 61, and an electric motor 62. The spring 60 and the damper 61 are provided in parallel between the vehicle body and the axle 4, and the motor 62 is provided on the upper portion of the damper 61. The damping force of the damper 61 as the suspension characteristic can be adjusted by controlling the output of the motor 62. Note that the specific configuration of the damping force variable damper 61 is disclosed in, for example, Japanese Patent Application Laid-Open No. 06-106950, and should be referred to if necessary.

  FIG. 2 is a block diagram showing the overall configuration of the control unit 7. As the control unit 7, a microcomputer mainly composed of a CPU, a ROM, a RAM, and an input / output interface can be used. The control unit 7 controls the output of the motor 62 based on the vertical load acting on the wheel 5, thereby controlling the damping force of the damper 61. Various detection signals are input to the control unit 7 in order to control the output of the motor 62.

  FIG. 3 is an explanatory diagram of the acting force acting on the wheel 5. The detection unit 8 detects the acting force acting on the wheel 5. For convenience of explanation, FIG. 2 shows only one block corresponding to the detection unit 8, but actually the detection unit 8 is provided corresponding to each wheel 5. The acting forces that can be detected by the detector 8 are a longitudinal force Fx, a lateral force Fy, and a vertical force Fz. The longitudinal force Fx is a component force generated in the direction parallel to the wheel center plane among the friction force generated on the ground contact surface of the wheel 5, and the lateral force Fy is a component force generated in a direction perpendicular to the wheel center plane. is there. On the other hand, the vertical force Fz is a force acting in the vertical direction, that is, a so-called vertical load. Each detection unit 8 is mainly configured by a strain gauge and a signal processing circuit that processes an electric signal output from the strain gauge and generates a detection signal corresponding to the acting force. Based on the knowledge that the stress generated on the axle 4 is proportional to the acting force, the acting force is directly detected by embedding a strain gauge in the axle 4. The specific configuration of the detection unit 8 is disclosed in, for example, Japanese Patent Application Laid-Open Nos. 04-331336 and 10-318862, and should be referred to if necessary.

  The first sensor 9 detects various information (vehicle state quantities) indicating the vehicle state such as vehicle speed, acceleration, lateral acceleration, and yaw rate. On the other hand, the second sensor 10 detects various information (operation state amount) indicating the operation state of the driver, such as the depression amount of the brake pedal, the depression amount of the accelerator pedal, and the handle angle.

  When the microcomputer that is the control unit 7 is functionally grasped, the control unit 7 includes an estimation unit 70 and a control unit 71. The estimation unit 70 estimates the vertical load Fz (hereinafter referred to as “estimated load Fze”) acting on each wheel 5 based on the operation state quantity and the vehicle state quantity. The control unit 71 compares the detected vertical load Fz (hereinafter referred to as “detected load Fzd”) and the estimated load Fze with each of the motors 62 provided corresponding to the wheels 5 as a control target. Based on the comparison result, a predetermined control signal Sct is output to the motor 62.

  FIG. 4 is a flowchart showing a suspension control routine according to the present embodiment. The process shown in this flowchart is called at predetermined intervals and executed by the control unit 7. In the present embodiment, a processing procedure related to a single wheel 5 will be described, but the control unit 7 executes this processing procedure for all the wheels 5.

  First, in step 1, various detection values are read. The detection values read in step 1 are the detected load Fzd detected by the detection unit 8, the vehicle state quantity detected by the first sensor 9, and the operation state quantity detected by the second sensor 10. is there.

  In step 2, the estimated load Fze is specified. As a method for specifying the estimated load Fze, for example, a method using a vehicle motion model may be used. The vehicle motion model is obtained by modeling the behavior of the vehicle such as the yaw motion and roll motion of the vehicle in a certain traveling situation, and is generated in advance based on a motion equation relating to the vehicle or through experiments and simulations. With this vehicle motion model, the current vehicle body posture is specified from the current vehicle state quantity. Further, the estimated load Fze of the wheel 5 considering the load movement due to the operation is specified by adding the operation state quantity by the driver to the specified vehicle body posture. Therefore, the ROM of the control unit 7 stores a map that describes the correspondence between the vehicle state quantity and the operation state quantity and the estimated load Fze. These correspondences are set in advance through experiments and simulations.

  The estimated load Fze is specified based on the vehicle specifications (vehicle weight, height of the center of gravity, wheel bale, etc.) stored in advance and / or the longitudinal force Fx and the lateral force Fy that are detection results. Is also possible. That is, the estimated load Fze may be specified in consideration of the load movement by estimating the vehicle state quantity based on these parameters.

  In step 3, it is determined whether or not a value obtained by subtracting the detected load Fzd from the estimated load Fze is a positive value. If a negative determination is made in step 3, that is, if the estimated load Fze is less than or equal to the detected load Fzd (Fze−Fzd ≦ 0), the process proceeds to step 4. On the other hand, if an affirmative determination is made in step 3, that is, if the estimated load Fze is greater than the detected load Fzd (Fze−Fzd> 0), the process proceeds to step 5.

  In step 4, it is determined whether or not a value obtained by subtracting the detected load Fzd from the estimated load Fze is a negative value. If an affirmative determination is made in step 4, that is, if the estimated load Fze is smaller than the detected load Fzd (Fze−Fzd <0), the process proceeds to step 6. On the other hand, if a negative determination is made in step 4, that is, if the estimated load Fze and the detected load Fzd match (Fze−Fzd = 0), the routine is exited.

  In step 5, a predetermined control signal Sct is output to the motor 62, and the output control of the motor 62 is performed so that the damping force of the damper 61 is larger than the current state. On the other hand, in step 6, a predetermined control signal Sct is output to the motor 62, and the output control of the motor 62 is performed so that the damping force of the damper 61 becomes smaller than the current state. As the output control method in these steps 5 and 6, the step value is added to (or subtracted from) the current output value so as to reduce the difference between the detected load Fzd and the estimated load Fze, or PID (Proportional) Integral and Derivative) control can be used.

  FIG. 5 is an explanatory diagram showing changes in the vertical load on the outer wheel side during steering. In the figure, the time course of the estimated load Fze is indicated by a dotted line, and the time course of the detected load Fzd is indicated by a solid line and a broken line. A solid line detection load Fzd is a transition of a detection value by a direct method corresponding to the detection method of the present embodiment, and a broken line detection load Fzd is a detection value based on a change in suspension stroke, that is, an indirect method. It is a transition of the detection value by. As can be seen from the figure, the detection load Fzd by the indirect method tends to be delayed in the rise of the detection value compared to that by the direct method. This is because the indirect detected load Fzd is a response compared with the direct detected load Fzd because the change in the vertical load is specified after the vehicle body changes its posture, that is, after the stroke amount of the suspension 6 changes. This is because the nature is low. On the other hand, when the driver performs an operation, the estimated load Fze can identify the load movement associated with the estimated load Fze earlier than the actual load movement.

  Therefore, in the present embodiment, the damping force of the damper 61 is controlled so as to reduce the difference between the current load (that is, the detected load) Fzd and the estimated load Fze. For example, when a steering operation is performed by a driver during cornering, the estimated load Fze of the outer wheel 5 is larger than the detected load Fzd, and the estimated load Fze of the inner wheel 5 is smaller than the detected load Fzd. Become. In this case, the damping force of the damper 61 on the outer ring side is increased, and a force against the displacement toward the contraction side is generated in the suspension 6 on the outer ring side (therefore, the sinking of the vehicle body is suppressed). On the other hand, the damping force of the damper 61 on the inner ring side is reduced, and a force against the displacement toward the extension side is generated in the suspension 6 on the inner ring side (therefore, lifting of the vehicle body is suppressed). Thereby, since the change in the posture of the vehicle body during cornering or acceleration / deceleration is suppressed, it is possible to improve the operability.

  Further, when overcoming road surface irregularities, the estimated load Fze is smaller than the detected load Fzd. This is because the estimation calculation based on the vehicle motion model reproduces the vehicle behavior assuming a steady state, and thus the estimated load Fze does not reflect the influence of the unevenness of the road surface. In this case, the damping force of the damper 61 of the wheel 5 overcoming the unevenness is reduced, and the suspension 6 is given a force that resists the displacement toward the expansion side, that is, a force that allows the displacement toward the contraction side. Thereby, since the attitude | position change accompanying road surface unevenness | corrugation is suppressed, while being able to aim at improvement in riding comfort, the road surface followability of the wheel 5 can be improved.

  Further, in the present embodiment, the vertical load Fz can be detected with high responsiveness compared to the indirect method because the vertical load Fz is directly detected. Therefore, by performing control based on the detected load Fzd, which is a direct detection value, suspension control with higher responsiveness than conventional can be performed.

  According to the present embodiment, when the estimated load Fze is specified, the operation state quantity is used in addition to the vehicle state quantity. Thereby, the behavior of the vehicle can be estimated at the timing corresponding to the operation of the driver. For this reason, the estimated load Fze can be identified earlier, and control can be improved by performing control using this value Fze. In the present embodiment, the estimated load Fze is specified using a map, but this value may be calculated by real-time processing. Further, when specifying the estimated load Fze, it is possible to specify only the vehicle state quantity without using the operation state quantity.

  The estimated load Fze may be specified based on at least the longitudinal force Fx or the lateral force Fy and vehicle specifications. Since the forces acting on the wheels 5 are directly reflected in these detected values Fx and Fy, it is possible to estimate the vehicle state quantity with high responsiveness, and thereby estimate the estimated load Fze with high accuracy. It becomes possible. Further, by using the detection result of the detection unit 8, it is possible to estimate the vehicle weight, the center of gravity height, and the like, which are vehicle specifications. Therefore, according to such a method, even if the vehicle specifications change over time, this can be estimated in real time, and the estimation accuracy of the estimated load Fze can be improved. .

  In this embodiment, the damping force of the damper 61 is used as a method for adjusting the suspension characteristics. However, the present invention is not limited to this, and the spring force of the suspension 6 may be adjusted. Specifically, when the estimated load Fze is larger than the detected load Fzd, the spring force is made larger than the current state, and a force against the displacement toward the contraction side is generated in the suspension 6. On the other hand, when the estimated load Fze is smaller than the detected load Fzd, the spring force is made smaller than the current state, and a force against the displacement toward the extension side is generated in the suspension 6. Even with such spring force adjustment, the same effect as the above-described damping force adjustment can be obtained. Note that the spring force can be adjusted by extending or shortening the length of the spring 60. That is, when the spring 60 is extended, the spring force increases, and when the spring 60 is contracted, the spring force decreases. The specific configuration for expanding and contracting the spring 60 is disclosed in, for example, Japanese Patent Application Laid-Open No. 05-38922, so refer to it if necessary. In this case, an air suspension may be used as the suspension 6 and the length of the air suspension may be expanded and contracted by adjusting the flow rate in the cylinder.

  In the present embodiment, the detection unit 8 is configured to detect the acting force acting in three directions as the acting force, but the present invention is not limited to this and acts in the necessary component force direction. It is sufficient if the acting force can be detected. Further, a six-component force meter that detects a six-component force including moments around these three directions may be used. Even in such a configuration, at least the acting force necessary for the control can be detected, so there is no problem. In addition, about the method of detecting the six component force which acts on the wheel 5, since it is disclosed by Unexamined-Japanese-Patent No. 2002-039744 and Unexamined-Japanese-Patent No. 2002-022579, please refer if necessary.

  Moreover, although this embodiment demonstrated the case where the detection part 8 was embed | buried under the axle shaft 4, this invention is not limited to this, Other variations can also be considered. From the viewpoint of detecting the acting force, for example, the detection unit 8 may be provided on a member that holds the wheel 5, such as a hub or a hub carrier. Note that the method of providing the detection unit 8 in a hub or the like is disclosed in Japanese Patent Application Laid-Open No. 2003-104139, and should be referred to if necessary.

Explanatory drawing of the vehicle to which the suspension device of this embodiment is applied Block diagram of suspension system Illustration of acting force The flowchart which shows the suspension control routine concerning this embodiment Explanatory drawing showing an example of change in vertical load on the outer ring side during steering

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Automatic transmission 3 Differential apparatus 4 Axle 5 Wheel 6 Suspension 60 Spring 61 Damper 62 Motor 7 Control unit 70 Estimation part 71 Control part 8 Detection part 9 1st sensor 10 2nd sensor A Suspension apparatus

Claims (8)

In the suspension device,
Suspension that can adjust the suspension characteristics that affect the posture change of the car body while suspending the wheel,
A detection unit that directly detects a vertical load acting on the wheel;
A first sensor for detecting a vehicle state quantity indicating a state of the vehicle;
An estimation unit that estimates the vertical load from the detected vehicle state quantity based on a vehicle motion model that models the behavior of the vehicle;
A suspension device comprising: a control unit that compares the detected vertical load with the estimated vertical load and controls the suspension characteristics based on the comparison result. In the suspension device,
Suspension that can adjust the suspension characteristics that affect the posture change of the car body while suspending the wheel,
A detection unit that directly detects longitudinal force, lateral force and vertical load acting on the wheel;
An estimation unit that estimates the vertical load by estimating a vehicle state quantity indicating a vehicle state based on vehicle specifications and at least the detected longitudinal force or the detected lateral force;
A suspension device comprising: a control unit that compares the detected vertical load with the estimated vertical load and controls the suspension characteristics based on the comparison result.   The control unit, when the detected vertical load is smaller than the estimated vertical load, controls the suspension characteristics so that the suspension resists displacement toward the contraction side, and from the estimated vertical load 3. The suspension device according to claim 1, wherein when the detected vertical load is large, the suspension characteristics are controlled so that the suspension resists displacement toward an extension side. 4. The suspension has a damper capable of adjusting a damping force as the suspension characteristic,
When the detected vertical load is smaller than the estimated vertical load, the control unit increases the damping force of the damper from a current state, and the detected vertical load is greater than the estimated vertical load. The suspension device according to any one of claims 1 to 3, wherein when the load is large, the damping force of the damper is made smaller than the current state as the suspension characteristic. The suspension is a suspension capable of adjusting a spring force as the suspension characteristic,
When the detected vertical load is smaller than the estimated vertical load, the control unit increases the spring force from a current state, and the detected vertical load is greater than the estimated vertical load. The suspension device according to any one of claims 1 to 3, wherein when it is large, the spring force is made smaller than a current state. A second sensor for detecting an operation state quantity of the driver;
The said estimation part estimates the said perpendicular | vertical load based on the said vehicle state quantity mentioned above and the said detected operation state quantity, It was described in any one of Claim 1 to 5 characterized by the above-mentioned. Suspension device. In the suspension control method,
A first step for directly detecting a vertical load acting on the wheel;
A second step of detecting a vehicle state quantity indicating the state of the vehicle;
A third step of estimating the vertical load from the detected vehicle state quantity based on a vehicle motion model that models the behavior of the vehicle;
A fourth step of comparing the detected vertical load with the estimated vertical load, and controlling suspension characteristics that affect a change in posture of a vehicle body of a suspension that suspends a wheel based on the comparison result; A suspension control method comprising:   In the fourth step, when the detected vertical load is smaller than the estimated vertical load, the suspension characteristics are controlled so that the suspension resists displacement toward the contraction side, and the estimated vertical load is determined. 8. The suspension control method according to claim 7, wherein when the detected vertical load is larger than a load, the suspension characteristic is controlled so that the suspension resists displacement toward an extension side. .

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